Apparatus for forming fiber preforms

ABSTRACT

A fiber preform for use in bag molding, fiber-reinforced molded resin articles is disclosed. The preform is a unitary, seamless, porous structure comprising short lengths of fibers which are bonded together by a resin binder. The preform has thickened areas which define zones of greater reinforcement for a finished structure. A machine for fabricating such a preform is also disclosed. The machine includes a screen form which is mounted within a surrounding vacuum chamber for rotation about its longitudinal axis. A fiber dispenser or cutter is mounted for movement in an axial direction with respect to the screen form but in a path corresponding to but spaced from the inner longitudinal profile of the screen form. The cutter is movable at a predetermined variable rate so that the wall thickness of the fibers may be varied to provide zones of greater fiber reinforcement. A resin binder spray gun follows the cutter along its path. The fibers are thrown against the screen by the cutter and are held in place by suction and by the binder. The binder is then cured by heat and the cured preform is removed from the screen by raising the screen from the vacuum chamber and then tilting the screen for easy access by an operator.

United States Patent Wiltshire [54] APPARATUS FOR FORMING FIBER PREFORMS[72] Inventor: Arthur J. Wiltshire, Cleveland,

Ohio 0 [73] Assignee: Structural Fibers, Inc., Chardon,

Ohio

[22] Filed: May 14,1970

[21] Appl. No.: 37,173

[52] US. Cl. ..425/80, 425/449, 425/405, 264/128, 264/114, 264/DIG. 78,425/439,

[5 1] Int. Cl. ..B29c 5/02, B296 5/04 [58] Field of Search..l8/5 R, 26RR, 30 GA, 30 GM, 18/30 GR, DIG. 50, DIG. 60; 264/91, 114,

[451 Aug.-29, 1972 39/22359 10/1964 Japan ..18/26 RR Primary Examiner-R.Spencer Annear Attorney-McNenny, Farrington, Pearne and Gordon [57]ABSTRACT A fiber preform for use in bag molding, fiber-reinforced moldedresin articles is disclosed. The preform is a unitary, seamless, porousstructure comprising short lengths of fibers which are bonded togetherby a resin binder. The preform has thickened areas which define zones ofgreater reinforcement for a finished structure. A machine forfabricating such a preform is also disclosed. The machine includes ascreen form which is mounted within a surrounding vacuum chamber forrotation about its longitudinal axis. A fiber dispenser or cutter ismounted for movement in an axial direction with respect to the screenform but in a path corresponding to but spaced from the innerlongitudinal profile of the screen form. The cutter is movable at apredetermined variable rate so that the wall thickness of the fibers maybe varied to provide zones of greater fiber reinforcement. A resinbinder spray gun follows the cutter along its path. The fibers arethrown against the screen by the cutter and are held in place by suctionand by the binder. The binder is then cured by heat and the curedpreform is removed from the screen by raising the screen from the vacuumchamber and then tilting the screen for easy access by an operator.

8 Claims, 8 Drawing figures PATENTimuszs I972 SHEET 1 OF 3 v INVENTOR.ARTHUR J. W/L TSH/RE WW 5 A TTOR EYS PATENTEDmczs m2 SHEEY 3 OF 3INVENTOR. ARTHUR J. W/LTSH/RE Q/ss ATTO EYS APPARATUS FOR FORMING FIBERPREFORMS BACKGROUND OF THE INVENTION This invention relates to themanufacture of hollow,

particularly, to the manufacture of fiber preforms which are to beimpregnated with a curable resin to form the finished tank. In themanufacture of such articles, randomly oriented fibers are formed in theapproximate shape of the article to be molded and held in that shape bya resin binder. The form is then encased within a rigid mold casing. Anexpandable bag, which will define the shape of the finished article, isplaced within the laid-up form in the mold. The form is held in place inthe mold by a suitably moderate pressure by expanding the bag to holdthe fiber form in place against the mold, and then the fiber form ispartially permeated with a thermosetting resin or the like. The bag issubsequently expanded by further inflation to compress the fiber form insuch a manner as to distribute the resin throughout the matting andachieve the results of pressure molding, while at the same time avoidingmigration of the fibers and destruction of the laid-up form.

The above-described process is set forth in US. Reissue Pat. No. 25,241to Randolph. In the Randolph patent, the fiber form comprises a flatsheet of fiber matting which is wrapped into a cylindrical form todefine the sidewall of a cylindrical tank. The top and bottom portionsof the fiber form comprise preformed fiber caps. According to theteachings of Randolph, therefore, a longitudinal overlap or seam isformed by the sidewall matting and such a seam results in an unevennessin the amount of fiber-reinforcing material along the longitudinaloverlapping portion of the matting. Further, since the end preforms areseparately formed, an overlapping joint is required between the sidewallmat and the preforms. Here again, an irregularity in the amount ofreinforcing material is present at the overlapping joints. Stillfurther, the lapping of the joints does not provide a uniforminterlocking of the fibers in the area of the lap.

In order to overcome the above problems, a technique is disclosed forforming a fiber preform having a tubular section and an integral endthereon wherein the fibers forming the preform are uniformly distributedalong the entire preform so that the final product provides a uniformhigh strength without excessive amounts of fiber in any location, and sothat a finished article has no more than one seam. This technique is setforth in copending US. application Ser. No. 742,692, which is assignedto the same assignee as the present invention.

According to the procedure of the above-identified application, anelongated screen form is rotated about its longitudinal axis. A vacuumis applied to the interior of the screen form to draw air into the formwhile a large number of randomly oriented chopped pieces of fiber aredirected against the rotating form by a roving cutter which traversesthe length of the form. The cutter is followed by a thermosetting resinbinder spray to lock the fibers in place. The binder-impregnated fibersare then subjected to heat to cure the binder.

Although this technique overcomes the problems associated with aplurality of lap seams and reduces the expense of the form byeliminating the need for sidewall matting, it has been found that aconsiderable portion of the fibers is lost, since the screen form doesnot capture all of the fibers on its sidewall. Furthermore, thetechnique is limited to the production of a fiber preform having asubstantially uniform sidewall thickness. In many tank applications, itis desirable to provide a tank having thickened wall sections so thatthose thickened sections will provide additional reinforcement andthread areas for tapped holes. The aforementioned technique is alsolimited to the production of articles having substantially straightsidewalls so that the finished preform may be removed from the screenform.

SUMMARY OF THE INVENTION This invention overcomes many of the problemsassociated with techniques according to the aboveidentified patent andaccording to the above-identified application. Specifically, thisinvention permits the fabrication of fiber preforms having either auniform thickness or zones of thickened wall sections so that threadedopenings may be provided in the finished article. Moreover, according tothe teachings of this invention, preforms may be fabricated which arecylindrical or which have non-linear sidewalls, e.g., hemisphericalpreforms which may be employed in the formation of spherical,fiber-reinforced plastic tanks.

In accordance with this invention, chopped fibers are deposited by adispenser such as a roving cutter along the inside surface of a rotatingscreen form. The dispenser moves in an axial direction relative to thescreen form and closely follows the contour of the form while the formitself is rotated about its axis. The fibers are thrown against thescreen form by the action of the cutter and are held against therotating screen form by enclosing the outside surface of the form in avacuum chamber.

In the preferred embodiment disclosed herein, a cylindrical screen formhaving a closed screen bottom is disposed so that its longitudinal axisextends vertically and the screen form is rotated about its verticalaxis at a speed less than the speed required to hold the fibers againstits inside surface by centrifugal force. A roving cutter assembly ispositioned within the screen and is caused to follow the contour of thescreen from a point spaced above the lowermost portion of the screen andalong a path which is spaced a uniform distance from the contour of thescreen toward the top of the screen. The path followed by the rovingcutter is determined by a preselected cam and cam follower assemblychosen for a particular application. In the process of cutting theroving, the chopped fiber is thrown toward the screen by the action ofthe cutter and is held in place by a vacuum chamber which surrounds theoutside surface of the screen. After depositing fiber at the bottom ofthe screen, the cutter assembly is gradually withdrawn at apredetermined rate to deposit fibers along the sidewall of the screen asthe screen rotates.

Also in accordance with the preferred embodiment disclosed herein, atwo-station machine is provided. The two-station machine includes twovacuum chambers each surrounding its own screen form. A cutter andbinder dispensing assembly is provided which deposits chopped fibers andbinder in one screen form while the other screen form, which containsbindercoated fibers, is subjected to heat by the application of aheating hood to the top of the form. After the heated preform is cured,the screen form is lifted from the vacuum chamber by a preform lift andconveyor device and then presented to the operator so that the preformcan be removed. The screen is presented to the operator in such a mannerthat it may be cleaned and reinserted into the vacuum chamber for thenext preforming operation.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a plan view of the preformmachine according to this invention, with certain duplicate partseliminated for clarity;

FIG. 2 is a partial section taken along the line 22 in FIG. 1;

FIG. 3 is an enlarged sectional view of a portion of the machine, theplane of the section being indicated by the line 3-3 in FIG. 1;

FIG. 4 is a cross sectional view similar to FIG. 3 but showing a cuttercontrol assembly for forming hemispherical preforms;

FIG. 5 is a sectional view of a hemispherical preform made in theembodiment shown in FIG. 4 illustrated in mating relationship with asimilar preform to provide a spherical preform;

FIG. 6 is a sectional view similar to FIG. 2 but showing the cutterassembly removed and showing the screen form removed by a screen liftassembly;

FIG. 7 is a view of a portion of the assembly shown in FIG. 6, the planeof the view being indicated by the line 77 in FIG. 6; and

FIG. 8 is a plan view of the conveyor shown in FIGS. 6 and 7.

Referring now to the drawings in greater detail, a platform or worksurface 11 supports first and second preforming stations 12 and 13,respectively. Mounted on the platform is a hood 17 arranged to swivelwith respect to the platform 11.

A control lift assembly 15 is mounted at the rear of the frame. Asimilar control lift assembly (not shown) is provided for the station13.

Each control lift assembly 15 includes a vertical post support 16.Mounted on the post support 16 is a lift cam 18 driven by a motor M anda suitable reduction drive D. The motor M is a variable speed reversingmotor controlled by a control device (not shown) wherein the speed ofrotation of the lift cam 18 can be varied and be reversed for a purposewhich will hereinafter become apparent.

The lift cam 18 has a cam follower linkage comprising a support bracket19 fixed to the support 16, links 21 and 22, and a sliding support post25. A cam follower roller 23 is journalled for rotation on the link 22and the link 22 is pivotally connected at one end to the link 21. Thelink 21 is, in turn, pivotaily connected at one end to the supportbracket 19. The support post 25 is slidably received through a verticalbore 26 in the bracket 19 to guide the post 25 for vertical movement.The other end of the link 22 is pivotally connected to the post 25 by apivotal connection 27. The vertical support post 16 extends through andis fixed to the support bracket 19. The lower end of the vertical post16 is mounted in a bearing so that the post 16 may be rotated about itsvertical axis. The support post may be locked in the positionillustrated in FIGS. 1 and 2 by a suitable locking means not shown).

Rotation of the cam 18 in a counterclockwise direction, as viewed inFIG. 2, causes the link 22 to move the post 25 upwardly. Movement of thepost 25 is axial and to accommodate this axial movement, the pivotalconnection between the links 21 and 22 swings slightly to the left asviewed in FIG. 2.

A fiber and binder-dispensing assembly 28 is fixed to the lower end ofthe post 25. As will be seen most clearly in FIG. 3, the cutter assembly28 includes a cylindrical housing 29 having a hemispherical, closedbottom end portion 30. The top of the housing 29 is covered by a plate31. A pin 32 extends horizontally across the housing 29 and has a link33 pivoted to its mid-portion. One end of the link 33 carries a rovingcutter 34 and a binder spray nozzle 35. The other end of the link 33 ispivotally connected to a push rod 36 which is adapted to move downwardlyto pivot the link 33 in a counterclockwise direction about the pin 32.As the link 33 pivots in this manner, the roving cutter 34 and the spraynozzle 35 swing from their solid outline position illustrated in FIG. 3to the position illustrated in phantom outline in that Figure. Thecutter is mounted so that it faces a slot opening 37 in the end portionof the housing 29. The nozzle extends through the opening 37. Thoseportions of the slot 37 which are not faced by the cutter duringmovement of the cutter are covered by wing plates 38 and 39, which arefixed to the cutter head.

The push rod 36 is moved downwardly by a slotted cam 40. The cam 40includes a cam track 41, which receives a cam follower 42 mounted on oneend of the push rod 36. The cam 40 is fixed to a shaft 43, which isdriven by a reversing motor 44 through a suitable speed reducer 44a. Thelink 33 is swung in a counterclockwise direction by the push rod 36 whenthe shaft 43 is driven in a clockwise direction to cause the camfollower 42 to follow the track 41.

The roving S is fed through a flexible guide tube 45 to the cutter 34.The cutter 34 chops the roving R into short fiber lengths. The roving Smay be a continuous strand of glass fiber. Binder resin, such as athermosetting resin, is fed to the spray head 35 through a flexible hose46.

The stations 12 and 13 are each provided with a perforated formingscreen or mandrel 50. The screen has a cylindrical sidewall 51, which isopen at the top and which is closed at the bottom by a hemispherical end52. The open upper mouth of the screen 50 is provided with an annularflange 53 which carries a plurality of register pins 54. The registerpins 54 extend through registry holes which are provided in a supportingcollar at the top end of a rotatable drum 55. The drum 55 is mounted ona drive post 56 (FIG. 6), which is driven about its vertical axis by asuitable drive means (not shown). The drum 55, therefore, rotates thescreen 50 about its vertical axis. A vacuum chamber 57 encloses the drum55 and is connected to a vacuum source, such as a fan, by a duct 60.Slots 61 are provided in the drum 55 so that air is drawn through thescreen 50 by the vacuum source.

In operation, the screen 50 is rotated by the drum 55. The assembly 28is positioned within the screen 50 in the manner illustrated in FIG. 3.The cutter 34 and the reversing motor 44 are energized so that theroving S is chopped by the cutter and deposited at the lowermost end ofthe screen 50. In the embodiment illustrated in FIG. 3, the initialmovement of the cam 40 causes the cutter 34 to dwell in the positionillustrated in solid outline in FIG. 3, since an initial portion of thecam track 41 follows a fixed radius with respect to the pin 43. As thecutter operates, a binder resin is forced under pressure through thefeed tube 46 and through the nozzle 35 so that a light binding coatingof resin is deposited on the chopped fibers. As the cam 40 continues itsclockwise movement, the track 41 departs from its fixed radius andbegins to force the push rod 36 downwardly to rotate the link 32 in acounterclockwise direction to thereby lay up fibers along thehemispherical portion 52 of the screen 50. When the cutter 34 reachesthe position illustrated in phantom outline in FIG. 3, a projection 60aon the cam 40 strikes a limit switch L to energize the reversing motor32. When the reversing motor is energized, the cam 18 begins itscounterclockwise movement to raise the entire assembly 28 upwardly inthe previously described manner. As the assembly 28 is moved upwardly,the cutter 34 is in its position illustrated in phantom outline in FIG.3 so that fibers are deposited along the cylindrical sidewall portion 51of the screen 50. The cam 18 is provided with an end protuberance 18a sothat as the cutter 34 approaches the open end of the screen 50, thecutter is accelerated to form a tapered portion 62 on the preform.

It should be appreciated that the thickness of the preform being formedmay be held constant or may be varied by changing the design of the camsl8 and 40. It is usually desirable to provide a thickened end portion 63in the preform by the previously mentioned dwell of the cutter 34 sothat the thickened end portion may be bored and tapped to receive aconnection. Furthermore, it should be appreciated that the shape of thecam 18 may be varied to provide thickened sidewall portions, such as theportion 64. Such thickened sidewall portions provide zones ofreinforcement for bored and tapped side access openings. The fibers arethrown against the sidewall of the screen 50 by the mechanical action ofthe cutter, and are held in place by the vacuum drawn through the screen50 and, to some degree, by the uncured binder spray. Since the cuttermoves axially to follow the contour of the screen, and since the screenis rotating about its vertical axis, a helical path is traced by thecutter. The fibers are deposited on the sidewall of the screen in arandom orientation.

When the assembly 28 reaches a position wherein the preform is complete,a limit switch (not shown) on the pole 25 de-energizes the cutter 34 andthe resin pressure through the tube 46. The motor M is then deenergizedby a second limit switch (not shown) when the end of the assembly 28clears the level of the platform 11. After the motor M has beende-energized, the bearing 20 is unlocked and the assembly is swung outof the way.

The hood 17 is mounted in a bearing 70 so that an open mouth of the hood17 may be swung over the open mouth of the screen 50 at the station 12.The heating hood 17 is connected to a source of hot air which is drawnthrough the preform by the vacuum in the chamber 57. The binder resin isthereby cured and the hood is swung away from the mouth of the screen.

As may be seen most clearly in FIGS. 6 and 7, a screen lift assembly 71is mounted above each of the stations 12 and 13. Each assembly 71includes a pair of double-acting, fluid-actuated cylinders 72 and 73.The cylinders 71 and 72 have piston rods 75 and 76 which are pivotallyconnected to opposite sides of a screen lift frame 77. The screen liftframe 77 includes a pair of parallel beams 78 and 79 having plates 80and 81 fixed thereto. The plates 80 and 81 are respectively pivoted tothe piston rods 75 and 76 and the beams 78 and 79 are tied together bytie rods 82 and 83. The beams 79 may be moved toward or away from thebeam 78 by a spring-biased, quick-acting clamp 84 provided on the end ofeach rod 82 and 83. Thus, the beam 79 may be moved toward the beam 78and against stop nuts 85 on the rods 82 and 83 when the clamps 84 aretightened and the beam 79 may be moved away from the beam 78 byloosening the clamps 84.

The frame 77 further includes rollers on the beams 78 and 79, which areadapted to engage the periphery of a ring 91 which is provided on thescreen 50. Thus, the screen is engaged by the frame 77 by lowering therods 75 and 76 with the beams 78 and 79 in their unclamped position.When the rollers 90 are radially aligned with the flange 91, the beamsare moved together until the rollers engage the ring 91. The piston rods75 and 76 are then retracted to lift the screen 50 out of registry withthe drum 55. With the screen spaced above the drum, a conveyor cart isrolled between the lifted screen 50 and the drum 55. As may be seen inFIG. 8, the cart 100 comprises a platform 101 having wheels 102 whichare guided by tracks 103 and 104 between a retracted position to aposition spaced above the drum 55. The cart 100 may be moved along thetracks 103 and 104 by a piston 105 having a rod 106 connected to theplatform 101. The cart 100 further includes a wedge 107 which slopesdownwardly toward the axis of the drum 55 and the axis of the screen 50positioned above the drum.

With the cart in the position illustrated in FIG. 6, the screen 50 islowered so that the curved bottom portion 52 of the screen engages thewedge 107. Further lowering of the screen 50 causes the pistons 71 and72 to pivot about an upper pivotal connection 1 l0 and causes the screento assume the position shown in FIG. 7. In such a position, the screenengages a pair of rollers 11 1 of the cart 100. With the screen 50 inthis position, the operator can conveniently remove the preform from thescreen. The screen may be cleaned by the operator and, to facilitate thecleaning operation, the screen may be rotated relative to the frame 77and the cart 100.

After cleaning the screen is lifted by the pistons 71 and 72 until it isagain spaced above the cart 100. The cart is then retracted by thecylinder 105 and the screen is lowered into registry with the drum 55 sothat another preform may be formed.

Referring now to FIG. 4, a fiber and binderdispensing assembly 128 isfixed to the lower end of a post 129. The assembly 128 is employed toform hemispherical preforms which may be assembled within a sphericalmold to produce fiber-reinforced, spherical containers. To produce sucha spherical container, a

screen form 130 is employed. The screen form 130 includes ahemispherical portion 131 and a portion 132 formed on the same radius asthe portion 130 to provide a tapered lap seam in the assembled sphericalpreform lay up. Such an assembled preform lay-up 133 is shown in FIG. 5.The preform 133 includes a bottom preform 134 produced by the screenform 130 and a preform 135 produced by a similar screen form (notshown). The screen employed to form the preform 135 has a curvatureformed by a radius R which corresponds to the radius of curvature of thescreen form 130. The screen form employed to produce the preform 135,however, has a different radius of curvature R between a zone 136 and azone 137 so that the preform 135 has a tapered lap seam 138 which isreceived within a tapered lap seam 139 formed in the preform 134.

v To form the preform 134, a post 129 is lowered so that a fiber andbinder-dispensing assembly 128 is positioned within the screen form 130.The assembly 128 includes a cylindrical, upper housing 140 and aspherical end housing 141. The top of the housing 140 is covered by aplate 142. A pin 143 extends horizontally across the housing 141 inaxial alignment with a diameter of the housing 141. The pin 143 has alink 144 pivoted to its mid-portion and one end of the link 144 carriesa roving cutter 145 and a binder spray nozzle 146. The other end of thelink 144 is pivotally connected to a push rod 147, which is adapted tomove downwardly to pivot the link 144 in a counterclockwise directionabout the pin 143. As the link 144 pivots in this manner, the rovingcutter 145 and the spray nozzle 146 swing from their solid outlineposition illustrated in FIG. 4 to the position illustrated in phantomoutline in that Figure. The cutter 145 is mounted so that it faces aslot opening 148 in the housing 141. The nozzle 146 extends through theopening 148. Those portions of the slot 148 which are not faced by thecutter 145 during movement of the cutter are covered by wing plates 149and 150, which are fixed to the cutter head 145.

The push rod 147 is moved downwardly by a slotted cam 151. The cam 151includes a cam track 152, which receives a cam follower 153 mounted onone end of the push rod 147. The cam 151 is fixed to a shaft 154 whichis driven by a reversing motor 155 through a suitable speed reducer 156.The link 144 is swung in a counterclockwise direction by the push rod147 when the shaft 154 is driven in a clockwise direction to cause thecam follower 153 to follow the track 152.

A continuous filament, such as the roving R, is fed through a flexibleguide tube 157 to the cutter 145. The cutter 145 chops the roving R intoshort fiber lengths. The roving R may be a continuous strand of glassfiber. Binder resin, such as a thermosetting resin, is fed to the sprayhead 146 through a flexible hose 158.

The screen 130 may be mounted within a rotatabie drum similar to thedrum 55 so that register pins 159 on the screen form 130 cooperate withsuch a drum.

In operation, the screen 130 is rotated by its drum. The assembly 128 ispositioned within the screen 130 in the manner illustrated in FIG. 4.The cutter 145 and the reversing motor 155 are energized so that theroving R is chopped by the cutter and deposited at the lowermost end ofthe screen 130. In the embodiment illustrated, the initial movement ofthe cam causes the cutter to dwell in the position illustrated in solidoutline in FIG. 4, since an initial portion of the cam track 152 followsa fixed radius with respect to the pin 154. As the cutter operates, abinder resin is forced under pressure to the feed tube 158 and throughthe nozzle 146 so that a light binding coating of resin is deposited onthe chopped fibers. As the cam 151 continues its clockwise movement, thetrack 152 departs from its fixed radius and begins to force the push rod147 downwardly to rotate the link 144 in a counterclockwise direction,to thereby lay up fibers along the hemispherical portion 131 of thescreen 130.

The cam track 152 has a quick lift portion 160 which accelerates thedownward movement of the push rod 147 to form the tapered lap seam 139.When the cam 151 reaches the end of its travel after the lap seam 139has been formed, a projection 161 on the cam strikes a limit switch 162to thereby de-energize the cutter 145 and the spray head 146. Theassembly 128 is then retracted and the preform 134 is cured in themanner previously indicated.

Although a preferred embodiment of this invention is illustrated, it isto be understood that various modifications and rearrangements of partsmay be resorted to without departing from the scope of the invention.

I claim:

1. Apparatus for making fibrous preforms for use in moldingfiber-reinforced plastic articles, comprising a perforated form whichdefines the shape of the preform to be formed, said form having an openmouth, a vertically extending cylindrical sidewall, and a closed bottom, and having its outside surface substantially enclosed by a chamber,vacuum means in said chamber for drawing air through said form, adispenser of chopped fibers, means to rotate the dispenser and the formrelative to each other about an axis passing through the mouth of saidform, means for translating said dispenser along a path spaced aconstant distance from said bottom and said sidewall and extending froma location adjacent said axis, across said bottom, and upwardly alongsaid sidewall so that said dispenser follows the contour of said form,said dispenser being adapted to throw fibers against the wall of saidform, whereby the fibers are thrown against the entire wall of said formand are held there by the air drawn through said form.

2. Apparatus according to claim 1, wherein said dispenser includes meansto dispense a binder to intermix with said chopped fibers.

3. Apparatus according to claim 1, wherein said dispenser of choppedfibers includes a cutter operable to out long strands of fiber intochopped fiber pieces.

4. Apparatus according to claim 1, wherein said cylindrical sidewall isclosed by a hemispherical bottom portion.

5. Apparatus according to claim 1, including gripping means mountedabove said form adapted to grip an upper portion of said form and toremove said form from said chamber, means pivotally connected to saidgripping means to raise said form vertically out of said chamber, andmeans for tilting said removed form toward a horizontal position so thatthe preform may be removed from said form.

6. Apparatus for making fibrous preforms for use in moldingfiber-reinforced plastic articles, comprising a perforated form whichdefines the shape of the preform to be formed, said form having an openmouth, a vertically extending cylindrical sidewall, and a closed bottom,and having its outside surface substantially enclosed by a chamber,vacuum means in said chamber for drawing air through said form, afiber-dispensing assembly comprising a housing, said housing having ahemispherical, closed bottom end, a fiber dispenser pivoted for movementabout said bottom end and along a path spaced a constant distance fromsaid closed bottom, said bottom end having a slot therein coextensivewith the pivotal movement of said fiber dispenser so that fibers may bedispensed through said slot and toward said form to cover a firstportion of said fonn, push rod means for pivoting said fiber dispenseralong said path, first cam means for driving said push rod,

second cam means for lifting said assembly so that the fiber dispensermay throw fibers against remaining portions of said form, and means torotate the form about an axis passing through the mouth of said form.

7. Apparatus according to claim 6, including gripping means mountedabove said form adapted to grip an upper portion of said form and toremove said form from said chamber, means pivotally connected to saidgripping means to raise said form out of said chamber, and means fortilting said removed form toward a horizontal position for removal ofsaid preform.

8. Apparatus according to claim 6 wherein said first portion of saidform comprises a hemispherical portion.

2. Apparatus according to claim 1, wherein said dispenser includes meansto dispense a binder to inteRmix with said chopped fibers.
 3. Apparatusaccording to claim 1, wherein said dispenser of chopped fibers includesa cutter operable to cut long strands of fiber into chopped fiberpieces.
 4. Apparatus according to claim 1, wherein said cylindricalsidewall is closed by a hemispherical bottom portion.
 5. Apparatusaccording to claim 1, including gripping means mounted above said formadapted to grip an upper portion of said form and to remove said formfrom said chamber, means pivotally connected to said gripping means toraise said form vertically out of said chamber, and means for tiltingsaid removed form toward a horizontal position so that the preform maybe removed from said form.
 6. Apparatus for making fibrous preforms foruse in molding fiber-reinforced plastic articles, comprising aperforated form which defines the shape of the preform to be formed,said form having an open mouth, a vertically extending cylindricalsidewall, and a closed bottom, and having its outside surfacesubstantially enclosed by a chamber, vacuum means in said chamber fordrawing air through said form, a fiber-dispensing assembly comprising ahousing, said housing having a hemispherical, closed bottom end, a fiberdispenser pivoted for movement about said bottom end and along a pathspaced a constant distance from said closed bottom, said bottom endhaving a slot therein coextensive with the pivotal movement of saidfiber dispenser so that fibers may be dispensed through said slot andtoward said form to cover a first portion of said form, push rod meansfor pivoting said fiber dispenser along said path, first cam means fordriving said push rod, second cam means for lifting said assembly sothat the fiber dispenser may throw fibers against remaining portions ofsaid form, and means to rotate the form about an axis passing throughthe mouth of said form.
 7. Apparatus according to claim 6, includinggripping means mounted above said form adapted to grip an upper portionof said form and to remove said form from said chamber, means pivotallyconnected to said gripping means to raise said form out of said chamber,and means for tilting said removed form toward a horizontal position forremoval of said preform.
 8. Apparatus according to claim 6 wherein saidfirst portion of said form comprises a hemispherical portion.